A group of cyberattackers that emerged in 2010 and then went quiet has resurfaced and is targeting Japan's critical infrastructure, a security vendor said this week.

The attacks have targeted utilities and energy companies in Japan, as well as other companies in finance, transportation and construction, said Greg Fitzgerald, chief marketing officer at Cylance, which specializes in end-point protection.

The group appears to be based in Asia, and its methods and procedures suggest it may be linked to a nation state, Fitzgerald said.

Symantec detected signs of the group, which Cylance calls Operation Dust Storm, in 2010, Fitzgerald said. The group went quiet in March 2013, shortly after Mandiant -- the forenics investigative unit of FireEye -- published a lengthy report on APT 1, which the company believes to be an elite cyber unit of the Chinese army.

The attacks studied by Cylance were aimed exclusively at Japan, Fitzgerald said. The group has acquired upwards of 200 domain names for part of its command-and-control infrastructure, he said.

The aim doesn't appear to be to damage critical infrastructure along the lines of what recently happened in December to utilities in Ukraine. Cyberattacks knocked out power to tens of thousands of customers in incidents security experts have said highlight the vulnerability of Internet-connected critical infrastructure.

Rather, the group is focused on reconnaissance and espionage and maintaining long-term access to networks, Fitzgerald said.

Cylance has reached out to Japan's Computer Emergency Response Team, the country's national cybersecurity coordinator, with its findings. It has also published a report with technical information, including domain names and hashes of malware, that could help companies figure out if they've been compromised.

Those infected are thought to have fallen victim to spear phishing emails, or targeted messages containing malware attachments. Another possibility is so-called watering-hole attacks, where victims are persuaded to click on a link or visit a website that has been compromised, delivering the attacker's malware.

In 2014 through last year, the attackers were installing a backdoor called Zlib.

"The backdoor provided the attacker with the ability to upload and download files, enumerate files and drives, enumerate system information, enumerate and manipulate Windows services, enumerate and impersonate logon sessions, mimic keystrokes and mouse input, capture screenshots and execute shell commands," according to Cylance's report.

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